Tectonics in the Western Anatolian Extensional Province from sequence stratigraphic modeling of multichannel seismic data in the Gulf of Kusadasi
DESCRIPTION: This project will accomplish two goals. The first part of the project will create software for modeling stratigraphy, the layers of rock that accumulate in sedimentary basins around the world. The patterns of the sedimentary layers, or strata, depend on the complex interplay of changes in sea level, tectonics and the supply of sediments. The model will be appropriate for modeling stratigraphy over time scales of from 10,000 to millions of years, will be applicable to many settings, and made broadly available for use by other scientists. There is very limited publically available software for this type of stratigraphic modeling. The second part of the project will apply the new software package to an area off of western Turkey. This is an area where stretching of the crust is causing the land to sink and accumulate layers of sediment. Mapping of the layers by Turkish colleagues show a complex pattern of both subsidence and uplift of the bay over the last 1 million years due to faulting. Changes in sea level that shifted the coastline back and forth over the 100,000-year glacial cycles provide a framework for interpreting ages of the strata. We will model the stratigraphy to determine the tectonics and contribute to assessing the seismic hazard of this region. It has been subject to recent earthquakes up to M6 and historic earthquakes up to M7. The project will provide training for a young Turkish scientist, and a U.S. undergraduate student, adding to their abilities to quantitatively model stratigraphy and estimate tectonics. The Gulf of Kusadasi is one of the most seismically active regions of the Western Anatolian Extensional Province with active fault systems expressing N-S extension, E-W compression, and NE-SW and NW-SE strike slip. High-resolution Turkish multichannel seismic data image an extensional basin, the offshore extension of a rift cutting the area, and two uplifted zones at high angle to it. The preserved sediments contain thirteen stratigraphic sequences composed of prograding deltas with shingled clinoforms that have been correlated to glacioeustatic cycles going back to >1 Ma. The sequences are cut by faults with varied orientations, and they reveal associated patterns of subsidence and uplift. These deposits can thus be used to quantify the vertical motions and fault offsets, and thereby constrain the tectonics of the region. The sequences, interpreted as due to the 100,000 year glacio-eustatic cycles, provide a clear temporal framework for deciphering the tectonic and sedimentary history of the region. We propose to use a numerical sequence stratigraphic model to reproduce the stratal geometries and quantify the vertical motions over the last 1 Ma. In order to do the modeling, we will rewrite Sequence, a code for modeling stratigraphy at a sequence stratigraphic timescale. The calculated subsidence will be used to estimate the extension, after accounting for isostatic unloading by the extension and loading by the sediments. The results will determine whether the area is undergoing pure extension, pure shear, or a mixture of the two. The rates of faulting through time will be estimated and will indicate if the deformation is steady-state, waxing or waning. Quantitative estimates of deformation at this scale are necessary to understand the complex tectonics of the Aegean-Anatolian region, and to better evaluate the earthquake hazard.